[GFS computer model surface forecast map for 1AM with snow (blue) in the immediate I-95 corridor and rain (green) closer to the coast; map courtesy tropicaltidbits.com]
Low pressure will quickly ride up the east coast tonight along the Arctic frontal boundary zone that slipped through our region yesterday. An area of moisture associated with this developing low pressure system will push precipitation into the I-95 corridor at the end of the day and it will continue until after midnight. Initially, it’ll likely be a little too warm in the lower levels of the atmosphere for snow, but later this evening the precipitation should fall as all snow. A coating to an inch of snow is likely by late tonight across the northern and western suburbs along the I-95 corridor and even the big cities from DC-to-Philly-to-NYC can wake up to a touch of snow on grassy and other untreated surfaces. Watch for slick spots on the roads late tonight; especially, in the northern and western suburbs as temperatures should dip into the upper 20’s in some areas following the precipitation event.
The cold pattern that begins today will last through the weekend and right through next week. We’ll likely have to deal with another storm in the Mid-Atlantic region early next week. Odds favor rain in the immediate I-95 corridor for this next event late Sunday night and Monday, but it is a close call and it could be just cold enough for some type of mixture around here. No matter what happens with this next storm system at the beginning of next week, a new batch of Arctic air will flood into the Mid-Atlantic region on Tuesday following the storm and this next air mass will actually be colder than this week’s initial blast.
One final note: the early season cold has been quite incredible across the Rockies during the past few days with some temperatures 45 degrees below normal for this time of year. Casper, Wyoming reached -27°F early yesterday – their coldest temperature ever for November and we’re not even at the halfway point yet for the month. Denver, Colorado bottomed out at -14°F early today after being in the 70’s on Sunday – their 2nd coldest temperature ever in November. Finally, the average temperature earlier today across the continental US was 23.9°F which was the coldest reading since 1986 this early in the season.